Isolation, Total Synthesis and Anti-Diabetic Activity of Filiforidine from Cassytha filiformis

Abstract

Cassytha filiformis is a folkloric herbal medicine used to treat type 2 diabetes mellitus (T2DM). In this study, an oxidized aporphine alkaloid, designated as Filiforidine (3,10,11-trimethoxy-1,2-methylenedioxy-7-oxoaporphine), was isolated from C. filiformis, and its structure was elucidated through comprehensive spectroscopic analysis. Owing to its novel structure and significant glucose consumption activity, the total synthesis of Filiforidine was achieved for the first time. The key steps featured an electrophilic addition reaction, involving the reduction of a nitro group to an amino group with lithium tetrahydroaluminum, and a copper bromide-catalyzed oxidative aromatization reaction as well as a photocyclization reaction. Several experimental steps were optimized. Furthermore, a complex post-treatment method was developed, which reduced the column chromatography separation steps. Specifically, 2-(4-methoxybenzo[d][1,3]dioxol -5-yl) ethan-1-amine is salted with dilute hydrochloric acid. Cytotoxicity assay and glucose oxidase assay showed that Filiforidine had significant glucose consumption-promoting effects on HL-7702 cells at 0.625 μM, 1.25 μM, and 2.5 μM but without cytotoxicity. Therefore, Filiforidine might be a promising drug candidate for the treatment of diabetes.

Keywords: Cassytha filiformis; Filiforidine; diabetes; total synthesis.

Figure 1

Structure of Filiforidine.

Figure 2

¹H-¹HCOSY (thick line) and HMBC (arrow) correlations of Filiforidine.

Figure 3

Retrosynthetic analysis of Filiforidine.

Figure 4

Conditions: (a) CH₂I₂, K₂CO₃, DMF, 150–160 °C, 75.0%; (b) C₃H₉ClSi, NaI, CH₃CN, 0–82 °C, 87.6%; (c) PFA, MgCl₂, TEA, 65–82 °C, 78.0%; (d) NaH, CH₃I, DMF, 20–30 °C, 82.0%; (e) CH₃NO₂, NH₄OAc, HOAc, 118 °C, 87.0%; (f) LiAlH₄, THF, 0–30 °C, 73.3%.

Figure 5

Conditions: (g) NaH, CH₃I, DMF, 0–10 °C, 86.0%; (h) NaBH₄, THF/MeOH, 20–30 °C, 91.2%; (i) SOCl₂/DMF, TCM, 60–70 °C, 97.5%; (j) TMSCN, Pd (OAc)₂, K₂CO₃, 80 °C, 76.2%; (k) NaOH, EtOH; reflux, 88.5%.

Figure 6

Conditions: (l) EDC/HOBt, DMF, 20–30 °C, 76.8%; (m) POCl₃, CH₃CN, reflux, 87.4%; (n) CuBr₂, DBU, DMSO, 20–30 °C, 78.9%; (o) (1) NaBH₄, MeOH; (2) 450 W high-pressure mercury lamp (λ = 310 nm); (3) air, 25 °C, 49.0%.

Figure 7

The effects of Filiforidine on glucose in vitro. Glucose consumption values are the means ± SD, n = 5, ** p < 0.01 or *** p < 0.001 vs. DMSO.

Figure 8

Effects of Filiforidine on cell viability in vitro. HL-7702 cells were incubated with DMSO or Filiforidine at the corresponding concentration for 24 h, and viability was tested by MTT staining. All values are presented as the means ± SD, *** p < 0.001 vs. DMSO.